The present disclosure relates to a differential transformer-based permeability sensor that detects a magnetic substance, and more particularly to a technique to adjust a sensor.
In an image forming apparatus that utilizes electrophotography, for example, a differential transformer-based permeability sensor is employed to detect toner concentration and a residual amount of magnetic toner in a two-component developer, or whether the toner is still available. The differential transformer-based permeability sensor includes a plurality of coils, and in many cases the coils are formed in a helical shape on a substrate or a multilayer substrate, thus to have a minimized thickness.
The coil formed on a substrate or a multilayer substrate may produce an error in an output of the sensor owing to a dimensional error in the manufacturing process, and therefore the sensor has to be adjusted. For such adjustment, for example, the wire constituting the outermost circumference of the helical coil is branched into a plurality of branch lines, such that an amount of magnetic flux in each of the branch lines differs from each other, and one of the branch lines is selected.